1. Field of the Invention
The present invention relates to a holder for holding a substrate such as a mask or a wafer, such substrates, a stage apparatus for holding and moving the holder, and an exposure apparatus for performing exposure processing using a mask and a substrate held by the stage apparatus. Moreover, the invention relates to a scanning exposure apparatus for performing exposure while moving the stage.
2. Description of the Related Art
Heretofore, various exposure apparatus have been used when manufacturing semiconductor devices or liquid crystal display devices by a lithography process. Presently however, projection exposure apparatus are typically being used, which transfer a pattern image of a photo mask or a reticle (hereinafter, generally referred to as xe2x80x9creticlexe2x80x9d) onto a substrate such as a wafer or a glass plate, on the surface of which a photosensitive material such as a photoresist or the like is applied, via a projection optical system. Recently, as such projection exposure apparatus, a so-called step and repeat type reduced size projection exposure apparatus (a so-called stepper) is becoming predominant. With this apparatus a substrate is mounted on a two-dimensionally moveable substrate stage, and the substrate is stepped by the substrate stage, to thereby repeat an operation for exposing a pattern image of the reticle onto each shot area on the substrate in sequence.
Recently a step and scan type projection exposure apparatus (a scanning exposure apparatus as described for example in Japanese Unexamined Patent Application, First Publication No. 7-176468) which is an improvement on a static type exposure apparatus such as the stepper, is being used to a considerable degree. The step and scan type projection exposure apparatus (scanning stepper) can expose a larger field with a smaller optical system, compared to the stepper. Hence there are merits in that production of the projection optical system is facilitated, that high throughput can be expected due to a decrease in the number of shots by using the large field exposure, that a balancing effect is obtained by scanning the reticle and the wafer relative to the projection optical system, and that improvement of the distortion and the depth of focus can be expected. Moreover, it is being said that as the degree of integration of the semiconductor device is increased from a DRAM of 16 MB (megabyte) to a DRAM of 64 MB, and further in the future, will be increased to 256 MB, and even to 1 GB (gigabyte) with time, a large field will become essential. Hence the scanning projection exposure apparatus will become predominant instead of the stepper.
In such a stepper or scanning stepper, a table which can be moved in the direction of the optical axis for adjustment of the focal position and is capable of leveling adjustment is installed on a stage. Then, a holder for attracting and holding a substrate, and a mobile mirror for reflecting the detection light are provided on the stage in a predetermined positional relationship. Detection light is then irradiated from a position detection device, such as a laser interferometer or the like arranged opposite to the mobile mirror, and a distance from the stage is measured based on the reflected light from the mobile mirror, to thereby detect the position of the substrate to a high precision. As for the reticle, in a similar manner, a mobile mirror is provided on a reticle stage that attracts and holds the reticle. Detection light is then irradiated from the position detection device, and a distance from the reticle stage is measured, to thereby detect the position of the reticle to a high precision.
As described above, with the integration of semiconductor devices, the circuits are being made finer, and the line width thereof is becoming highly precise in the order of sub-microns. Therefore, the precision required for such exposure apparatus for forming a circuit pattern as described above is increasing year after year, and positioning precision of for example 5 to 10 nm or less is required. Consequently, in the stage portion of the exposure apparatus, positioning precision of about 1 nm is required.
Conventionally, as one means for realizing such high-precision positioning, attempts have been made where the exposure apparatus is installed in a chamber, the temperature of which is strictly controlled, and the stages are separately installed in housings, the temperature of which is more strictly controlled. As a result, expansion and contraction of the stages due to the change in temperature is suppressed, and positioning error resulting from the temperature change is eliminated.
Moreover, as for the holder, in a condition with the substrate supported by a multiplicity of fine protrusions with tips lying in a single plane, an approximately closed off space between the holder and the substrate is reduced in pressure for attachment, thereby reducing the contact area between the holder and the substrate. As a result, a situation where the flatness of the substrate is deteriorated due to dust and dirt caught between the substrate and the holder can be prevented, thereby eliminating positioning error resulting from deterioration of flatness.
However, with the above described conventional stage apparatus and holder, and scanning exposure apparatus and exposure apparatus, problems as described below exist.
The diameter of substrates is being increased in order to improve production efficiency, and wafers having an outer diameter of about 300 mm have recently been developed and put to practical use. In this case, the distance between the center of the wafer and the mobile mirror becomes about 200 mm, and even if ceramics having a relatively small thermal expansion, such as alumina, silicon nitride or the like are used for the holder and the mobile mirror, as in the conventional case, it is necessary to control the atmosphere temperature at the stage portion to the order of 0.001xc2x0 C. in order to ensure positioning precision of 1 nm. Hence, there are such problems that cost relating to temperature control is significantly increased, and if the temperature control is out of order due to unforeseen circumstances, the possibility of the positioning precision not being satisfied increases.
In particular, in the case of an exposure apparatus that performs double exposure by using a plurality of reticles for high resolution exposure, two reticles for example are provided in a row and held on the reticle stage. However, there is a problem in that with the position measurement for the reticle on the far side from the mobile mirror in the row direction, the distance between the reticle and the mobile mirror is further increased. Hence higher precision temperature control is required.
Moreover, even if the atmosphere temperature is controlled within a predetermined range, and the contact area between the holder and the substrate is very small, the heat accompanying the exposure processing is applied to the holder via the substrate, resulting in thermal expansion. Therefore, if the substrate is subjected to exposure processing over a plurality of shot areas, the holder undergoes thermal expansion with the progress of the exposure processing. Hence, the expansion length becomes different between shot areas on the substrate, causing a problem in that high-precision superposition onto this layer becomes difficult for each shot area.
In view of the above situation, it is an object of the present invention to provide a stage apparatus and holder, and a scanning exposure apparatus and an exposure apparatus which can maintain positioning precision relative to the substrate, without excessively relying on the precision of temperature control.
To achieve the above described object, the present invention adopts the following construction.
The stage apparatus of the present invention comprises: a holder for holding a substrate, and a position detection device for detecting a position of the substrate, based on reflected light from a mobile mirror provided at a predetermined positional relationship with the holder, and the holder and a base material of the mobile mirror consist of ceramics having a coefficient of thermal expansion of 1xc3x9710xe2x88x926/xc2x0 C. or less.
Therefore, with the stage apparatus of the present invention, if the substrate and the mobile mirror are arranged at a distance of for example 200 mm, a variation in the atmosphere temperature of up to about 0.005xc2x0 C. can be allowed in order to ensure a positioning error of not larger than 1 nm due to temperature change. Accordingly, the degree of dependence on temperature control is reduced, enabling a reduction in costs. As a ceramics having such a low thermal expansion, a cordierite type ceramics is preferable. A cordierite type ceramics consists generally of a composition of 2MgO-2Al2O3-5SiO2, and is obtained by blending respective metal oxides at a predetermined ratio, molding these to a predetermined shape, and sintering in an oxidizing atmosphere at 1300 to 1550xc2x0 C. Moreover, with the stage apparatus, when a predetermined positioning precision is maintained, the effect is obtained in that the degree of dependence on temperature control can be alleviated and costs associated with temperature control can be reduced.
A stage apparatus in an other embodiment of the present invention is constructed such that the holder and the base material of the mobile mirror comprise a ceramics having a coefficient of thermal expansion of 0.5xc3x9710xe2x88x926/xc2x0 C. or less. With this stage apparatus, a variation in the atmosphere temperature of up to about 0.01xc2x0 C. can be allowed. Hence the effect is obtained in that the degree of dependence on temperature control can be further alleviated and costs associated with temperature control can be greatly reduced.
A stage apparatus in an other embodiment of the present invention is constructed such that a mobile mirror and a holder are held by a common base. With this stage apparatus, the effect is obtained in that thermal expansion of the mobile mirror and the holder held by the base, due to the temperature change can be kept low and the degree of dependence on temperature control can be alleviated.
A stage apparatus in an other embodiment of the present invention is constructed such that at least a part of the base is ceramics. With this stage apparatus, the effect is obtained in that stress resulting from a difference in the expansion length does not occur. Hence factors causing positioning error can be removed beforehand.
A stage apparatus in an other embodiment of the present invention is constructed such that a movable stage for integrally moving the mobile mirror and the holder is provided. With this stage apparatus, the effect is obtained in that thermal expansion due to the temperature change with respect to the moving mobile mirror and holder can be kept low. Hence the degree of dependence on temperature control can be reduced.
A stage apparatus in an other embodiment of the present invention is constructed such that at least a part of a movable stage is ceramics. With this stage apparatus, the effect is obtained in that the occurrence of a positioning error due to thermal expansion of the movable stage can be suppressed.
A stage apparatus in an other embodiment of the present invention is constructed such that a support member for movably supporting the movable stage is provided. With this stage apparatus, the effect is obtained in that the occurrence of a positioning error due to thermal expansion of the movable stage supported by the support member can be suppressed.
A stage apparatus in an other embodiment of the present invention is constructed such that at least of a part of the support member is ceramics.
As a result, with this stage apparatus, the effect is obtained in that the occurrence of a positioning error due to the thermal expansion of the support member can be suppressed. Moreover, even if the surface of the stage apparatus is damaged, since the surface does not protrude, an air pad such as a non-contact bearing or the like is not damaged. Hence high planar precision is maintained so that planar travel characteristics of the movable stage can be maintained for a long period of time. Moreover, since the ceramics are a non-magnetic material, when a magnetic bearing is used as a non-contact bearing, the ceramics do not adversely affect the magnetic bearing.
Furthermore, the holder of the present invention is a holder for holding a substrate, having a plurality of protruding members arranged at approximately even spacing for supporting the substrate, and the plurality of protruding members consist of ceramics having a coefficient of thermal expansion of 1xc3x9710xe2x88x926/xc2x0 C. or less.
Accordingly, with the holder of the present invention, even if heat is applied to the protruding members via the substrate due to the exposure processing or the like, a temperature change of up to about 0.007xc2x0 C. can be allowed in order to suppress a difference in the thermal expansion occurring in the substrate having, for example, a radius of 150 mm, so as to be not larger than 1 nm. Furthermore, with this holder, the effect is obtained in that even if heat is transmitted from the substrate, thermal expansion can be suppressed, and stress applied to the substrate can be reduced.
A holder in an other embodiment of the present invention is constructed such that the coefficient of thermal expansion of the protruding members is 0.5xc3x9710xe2x88x926/xc2x0 C. or less. With this holder, the effect is obtained in that thermal expansion can be further suppressed, and stress applied to the substrate can be further reduced. Moreover, temperature change of up to about 0.013xc2x0 C. can be allowed in order to suppress a difference in the thermal expansion occurring in a substrate having a radius of 150 nm, so as to be not larger than 1 nm. Therefore the degree of dependence on temperature control can be greatly reduced.
A holder in an other embodiment of the present invention is constructed such that the protruding members are surface-treated with silicon carbide (SiC). With this holder, the effects is obtained in that electroconductivity is improved, thereby enabling countermeasures against static electricity to be effected. Furthermore, the surface becomes dense thereby increasing the strength.
Moreover, the scanning exposure apparatus of the present invention is a scanning exposure apparatus for exposing a pattern on a substrate while a stage is moving, and comprises: a holder for holding the substrate, and a position detection device for detecting a position of the substrate, based on reflected light from a mobile mirror provided at a predetermined positional relationship with the holder, and the holder and a base material of the mobile mirror consist of ceramics having a coefficient of thermal expansion of 1xc3x9710xe2x88x926/xc2x0 C. or less.
Therefore, with the scanning exposure apparatus of the present invention, if the substrate and the mobile mirror are arranged at a distance of for example 200 mm, a variation in the atmosphere temperature of up to about 0.005xc2x0 C. can be allowed in order to ensure a positioning error of not larger than 1 nm due to temperature change. Accordingly, the degree of dependence on temperature control is reduced, enabling a reduction in costs. As a ceramics having such a low thermal expansion, a cordierite type ceramics is preferable. A cordierite type ceramics consist generally of a composition of 2MgO-2Al2O3-5SiO2, and is obtained by blending respective metal oxides at a predetermined ratio, molding these to a predetermined shape, and sintering in an oxidizing atmosphere at 1300 to 1550xc2x0 C. Moreover, with the scanning exposure apparatus, when a predetermined positioning precision is maintained, the effect is obtained in that it becomes possible to alleviate the degree of dependence on temperature control, enabling costs associated with temperature control to be reduced.
A scanning exposure apparatus in another embodiment of the present invention is constructed such that the holder and a base material of the mobile mirror consist of ceramics having a coefficient of thermal expansion of 0.5xc3x9710xe2x88x926/xc2x0 C. or less. With this scanning exposure apparatus, a variation in the atmosphere temperature of up to about 0.01xc2x0 C. can be allowed. Hence the effect is obtained in that the degree of dependence on temperature control can be further alleviated and costs associated with temperature control can be greatly reduced.
A scanning exposure apparatus in an other embodiment of the present invention is constructed such that the stage is a substrate stage for moving the substrate via the holder. With this scanning exposure apparatus, the effect is obtained in that also when positioning precision is maintained relative to the substrate on which a pattern is exposed, it becomes possible to alleviate the degree of dependence on temperature control, enabling a reduction in costs associated with temperature control.
A scanning exposure apparatus in an other embodiment of the present invention is constructed such that a plurality of the substrate stages are provided. With this scanning exposure apparatus, the effect is obtained in that throughput can be greatly improved by implementing the exposure operation while executing the substrate replacement and alignment operation.
A scanning exposure apparatus in an other embodiment of the present invention is constructed such that the stage is a mask stage for moving a mask. With this scanning exposure apparatus, the effect is obtained in that also when positioning precision is maintained relative to the mask on which a pattern is formed, it becomes possible to alleviate the degree of dependence on temperature control, enabling a reduction in costs associated with temperature control.
A scanning exposure apparatus in an other embodiment of the present invention is constructed such that the mask stage moves, holding a plurality of masks. With this scanning exposure apparatus, the effect is obtained in that even if the distance between the mask and the mobile mirror increases, it becomes possible to alleviate the degree of dependence on temperature control when positioning precision is maintained, enabling a reduction in costs associated with temperature control.
An exposure apparatus of the present invention is an exposure apparatus for exposing a pattern on a substrate, and is characterized in that the substrate is held by a holder having a plurality of protruding members arranged at approximately equal spacing, and the plurality of protruding members consist of ceramics having a coefficient of thermal expansion of 1xc3x97106/xc2x0 C. or less.
Accordingly, with the exposure apparatus of the present invention, even if heat is applied to the protruding members via the substrate due to the exposure processing or the like, a temperature change of up to about 0.007xc2x0 C. can be allowed in order to suppress a difference in the thermal expansion occurring in the substrate having, for example, a radius of 150 nm, so as to be not larger than 1 nm. Furthermore, with this exposure apparatus, the effect is obtained in that even if heat is transmitted from the substrate, it becomes possible to suppress the variation in the expansion length between a plurality of shot areas on the substrate, by reducing the stress applied to the substrate. Hence deterioration of superposition precision can be prevented beforehand.
An exposure apparatus in an other embodiment of the present invention is constructed such that the coefficient of thermal expansion of the protruding members is 0.5xc3x9710xe2x88x926/xc2x0 C. or less. With this exposure apparatus, the effect is obtained in that a temperature change of up to 0.013xc2x0 C. can be allowed, enabling a significant reduction in the degree of dependence on temperature control. Moreover, the stress applied to the substrate can be further reduced, enabling effective prevention of deterioration in the superposition precision.
An exposure apparatus in an other embodiment of the present invention is constructed such that the protruding members are surface-treated with silicon carbide (SiC). With this exposure apparatus, the effects is obtained in that electroconductivity is improved, thereby enabling countermeasures against static electricity to be effected. Moreover, the surface becomes dense thereby increasing the strength.